This invention relates to apparatus for the preparation of a body cross-sectional image utilizing ionizing rays in general and more particularly to an improved apparatus in which the output signals of a multiplicity of detectors which are coupled to electronic circuitry can be brought out of an image convertor or a cyrostat on a single common output line.
Apparatus is known for the preparation of a body cross-section image having picture elements which are derived from the absorption of ionizing rays which penetrate the corresponding body element in the body cross-section plane sequentially in different directions. In such apparatus a multiplicity of detectors arranged side by side in the body cross-section plane are utilized to detect the amount of absorption of the rays. The electrical output signals of the detectors are provided an inputs to electronic circuitry.
Arrangements of this general nature for the preparation of a body cross-section image in which the body is scanned by parallel displacement of the radiation source and the radiation receiver and the body cross-section plane are known as scanners. In such devices an X ray or gamma ray source generates a bundle of parallel rays which penetrate the body to be examined in the cross-section plane and a certain portion of which rays are absorbed by the body. An image detector or carrier is disposed behind the body to be examined with the radiation, which after a portion of it has been absorbed, strikes the image carrier. By means of a stepwise parallel displacement of the radiation source and image carrier, the body elements are scanned sequentially in a cross-sectional plane. Subsequently, the radiation source and the image carrier are tilted through a predetermined angle with respect to an axis extending perpendicular to the cross-section plane and the body part cross-section plane is again projected on the image carrier by parallel displacement. The individual picture elements are thus penetrated by the radiation in a different direction. If this process is repeated a number of times, each body element in the cross-section plane is imaged as many times as the system is tilted about the axis. The conversion of the different individual measurements of the body elements and their correlation to the corresponding picture element of the body cross-section image to be prepared are obtained by means of electronic circuitry in a computer which utilizes, for example, 28,800 equations with 6,400 variables to carry out the image processing.
In one particular embodiment of such a device, the fan shaped radiation of a radiation source is subdivided into individual ray bundles lying in the cross-sectional plane by means of separate collimators. This is done to shorten the time required to generate the data necessary to produce a body cross-section impage. Behind the body a plurality of photodetectors is provided having associated therewith a common reference scintillator. The output signals of the photomultipliers are further processed in electronic circuitry and then control a printer which furnishes the body cross-sectional image. Such as disclosed in German Offenleichenshaft 1,941,433. In the disclosed arrangement for the preparation of a body cross-section image using a fan shapped ray bundle and a plurality of detectors in the radiation receiver, each individual detector furnishes a separate output signal which is fed to the electronic circuitry for further processing.
Thus, for each detector a separate output line from the radiation receiver is therefore necessary. This requires considerable expense, particularly if the radiation receiver is operated in a vacuum or if semiconductor detectors which must be kept in a low temperature in a special cooling device are utilized, i.e., semiconductor detectors disposed in a cryostat.
In view of these problems with bringing out separate lines it is the object of the present invention to provide a simplified information readout for a multiple detector arrangement of this nature.